U.S. patent number 7,278,294 [Application Number 11/104,287] was granted by the patent office on 2007-10-09 for system and method for determining atomization characteristics of spray liquids.
Invention is credited to Durham Kenimer Giles, Russell Stocker.
United States Patent |
7,278,294 |
Giles , et al. |
October 9, 2007 |
System and method for determining atomization characteristics of
spray liquids
Abstract
A system and method for determining the atomization
characteristics of fluids being emitted by a nozzle is disclosed.
In one embodiment, a fluid is emitted through a nozzle while
simultaneously sensing vibrations occurring within the nozzle. The
vibrations provide information about the atomization
characteristics of the fluid. By comparing the sensed vibrations to
vibration patterns produced by known fluids through the same or a
similar nozzle, the atomization characteristics of the fluid being
tested can be predicted. In one embodiment, for instance, the
atomization characteristics of a fluid may be determined as a
function of velocity or flow rate through the nozzle.
Inventors: |
Giles; Durham Kenimer (Davis,
CA), Stocker; Russell (Davis, CA) |
Family
ID: |
37081856 |
Appl.
No.: |
11/104,287 |
Filed: |
April 12, 2005 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20060225489 A1 |
Oct 12, 2006 |
|
Current U.S.
Class: |
73/64.53;
73/53.01; 73/865.9 |
Current CPC
Class: |
G01N
29/032 (20130101); G01N 29/14 (20130101); G01N
29/222 (20130101); G01N 29/4427 (20130101); G01N
29/46 (20130101); B05B 12/082 (20130101); G01N
2291/02818 (20130101) |
Current International
Class: |
G01N
29/02 (20060101) |
Field of
Search: |
;73/64.53,53.01,865.9 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Sensing Spray Nozzle Vibration as a Means for Monitoring
Operation", by D.K. Giles, pp. 1-7, ILASS Americas, 17.sup.th
Annual Conference on Liquid Atomization and Spray Systems,
Arlington, VA, May 2004. cited by other .
Abstract of Article--Breakup length of forced liquid jets, Kalaaji
et al., Physics of Fluids, vol. 15, Issue 9, Sep. 2003, pp.
2469-2479. cited by other .
Abstract of Article--Controlling droplet deposition with polymer
additives, Bergeron et al., Nature, vol. 405(6788), Jun. 15, 2000,
pp. 772-775. cited by other .
Abstract of Article--Design Factors affecting Spray Characteristics
and Drift Performance of Air Induction Nozzles, Ellis, et al,
Biosystems Engineering, vol. 82, Issue 3, Jul. 2002, pp. 289-296.
cited by other .
Abstract of Article--Designing intelligent fluids for controlling
spray applications, Bergeron, C. R. Physique, vol. 4, Issue 2, Mar.
2003, pp. 211-219. cited by other .
Abstract of Article--Different Modes of Vortex Shedding: An
Overview, Zdravkovich, Journal of Fluids and Structures, vol. 10,
Issue 5, Jul. 1996, pp. 427-437. cited by other .
Abstract of Article--Effects of formulation on spray nozzle
performance for applications from ground-based boom sprayers,
Miller et al., Crop Protection, vol. 19, Issues 8-10, Sep. 12,
2000, pp. 609-615. cited by other .
Abstract of Article--How adjuvants influence spray formation with
different hydraulic nozzles, Ellis et al., Crop Protection, vol.
18, Issue 2, Mar. 1999, pp. 101-109. cited by other .
Abstract of Article--Instrumentation and start up of a new
elongational rheometer with a preshearing history, Rios et al.,
Review of Scientific Instruments, vol. 73, Issue 8, Aug. 2002, pp.
3007-3011. cited by other .
Abstract of Article--Mixing Characteristics of a Flapping Jet from
a Self-Exciting Nozzle, Mi et al., Applied Scieintific Research,
vol. 67, No. 1, 2001, pp. 1-23. cited by other .
Abstract of Article--Modification of a vortex street by a polymer
additive, Cressman et al., Physics of Fluids, vol. 13, Issue 4,
Apr. 2001, pp. 867-861. cited by other .
Abstract of Article--On vortex shedding behind a circular disk,
Miau et al., Experiments in Fluids, vol. 23, No. 3, Jul. 1993, pp.
225-233. cited by other .
Abstract of Article--Optimization of acoustic signals in a
vortex-shedding flowmeter using numerical simulation, von Lavante,
et al., International Journal of Heat and Fluid Flow, vol. 20,
Issue 4, Aug. 1999, pp. 402-404. cited by other .
Abstract of Article--Pulsed-jet Microspray Applications for High
Spatial Resolution of Deposition on Biological Targets, Downey et
al., Journal of the International Institutes for Liquid Atomization
and Spray Systems, vol. 14, Issue 2, 2004, 17 pages. cited by other
.
Abstract of Article--Squeezing flow viscometry for nonelastic
semiliquid food--theory and applications, Campanella et al., Crit.
Rev. Food Sci. Nutr., vol. 43, No. 3, 2002, pp. 241-264. cited by
other .
Abstract of Article--Suppression of Aerosol Generation During
Spraying and Deposition of Consumer Products, Giles et al., Journal
of the International Institutes for Liquid Atomization and Spray
Systems, vol. 15, Issue 4, 2005, pp. 423-438. cited by other .
Abstract of Article--Utility Adjuvants, McMullan, Weed Technology,
vol. 14, No. 4, 2000, pp. 792-797. cited by other .
Abstract of Article--Vortex Shedding from Bluff Bodies and a
Universal Strouhal Number, Nakamura, Journal of Fluids and
Structures, vol. 10, No. 2, Feb. 1996, pp. 159-171. cited by other
.
Abstract of Article--Vortex-Induced Vibrations of an Elastic
Circular Cylinder, Zhou et al., Journal of Fluids and Structures,
vol. 13, Issue 2, Feb. 1999, pp. 165-189. cited by other .
Article--Break-up dynamics and drop size distributions created from
spiraling liquid jets, Wong et al., International Journal of
Multiphase Flow, vol. 30, 2004, pp. 499-520. cited by other .
Article--Non-Newtonian viscous oscillating free surface jets, and a
new strain-rate dependent viscosity form for flows experiencing low
strain rates, Bechtel et al., Rheol Acta, vol. 40, 2001, pp.
373-383. cited by other .
Piezo Film Sensors Technical Manual from Measurement Specialties,
Inc., Appendices A and B, Apr. 1999, pp. 59-82. cited by other
.
Presentation--Spray Deposition and Drift From Two "Medium" Nozzles,
Hoffman et al., at the 2002 Joint ASAE/NAAA Technical Meeting,
Reno, NV. Paper No. 02-AA04. St. Joseph, MI. ASAE. cited by other
.
Product Data Sheet for AIM Command.RTM. Spray System (Case IH), 2
pages. cited by other .
Giles et al. U.S. Appl. No. 11/135,054, filed May 23, 2005,
Networked Diagnostic And Control System For Dispensing Apparatus.
cited by other .
Article--A new model to determine dynamic surface tension and
elongated viscosity using oscillating jet measurements, Bechtel et
al., J. Fluid Mech., vol. 293, 1995, pp. 379-403. cited by other
.
Article--Effects of spray adjuvants on swath patterns and droplet
spectra for a flat-fan hydraulic nozzle, Chapple et al., Crop
Protection, vol. 12, No. 8, 1993, pp. 579-590. cited by other .
Article--Measurement of Extensional Viscosity of Polymer Solutions
and its Effects on Atomization from a Spray Nozzle, R. W. Dexter,
Atomization and Sprays, vol. 6, 1996, pp. 167-191. cited by other
.
Article--Optimal Control of Vortex Shedding Using Low-Order Models.
Part I--Open-Loop Model Development, Graham et al., Int. J. Numer.
Meth. Engng., vol. 44, 1999, pp. 945-972. cited by other .
Article--Optimal Control of Vortex Shedding Using Low-Order Models.
Part II--Model-Based Control, Graham et al., Int. J. Numer. Meth.
Engng., vol. 44, 1999, pp. 973-990. cited by other .
Article--Aerial Spray Drift from Different Formulations of
Glyphosate, I. W. Kirk, Transactions of the ASAE, vol. 43, No. 3,
pp. 555-559. cited by other .
Article--A System for Determining Dynamic Surface Tension Using the
Oscillating Jet Technique, Reichard, et al., Atomization and
Sprays, vol. 7, 1997, pp. 219-233. cited by other .
Paper No. AA03-002 entitled Field Comparisons for Drift
Reducing/Deposition Aid Tank Mixes, Wolf, et al., for presentation
at the 2003 ASAE/NAAA Technical Session, Dec. 8, 2003. cited by
other .
Paper No. 03-21060 entitled Spray Mix Adjuvants for Spray Drift
Mitigation--Progress Report, I. W. Kirk for presentation at the
2003 ASAE Annual International Meeting, Jul. 27-30, 2003. cited by
other .
Paper No. 01-1102 entitled Spray Drift Estimates from Aerial Spray
Droplet Spectra, I. W. Kirk for presentation at the 2001 NAAA/ASAE
Joint Technical Session, Dec. 3, 2001. cited by other .
Paper entitled A Summary of Tank Mix and Nozzle Effects on Droplet
Size by Spray Drift Task Force, 2001, 5 pages. cited by
other.
|
Primary Examiner: Williams; Hezron
Assistant Examiner: Frank; Rodney
Attorney, Agent or Firm: Dority & Manning, PA
Claims
What is claimed is:
1. A method for determining the atomization characteristics of a
fluid being emitted by a nozzle comprising: emitting a fluid from a
nozzle at controlled conditions; sensing vibrations occurring
within the fluid nozzle while the fluid is being emitted; comparing
the sensed vibrations to the vibrations of a known reference fluid
having known atomization properties for determining the relative
atomization properties of the fluid being emitted from the nozzle;
and sensing a fluid pressure drop over an orifice while the fluid
is being emitted from the nozzle, the pressure drop being used to
determine a fluid shear viscosity of the fluid.
2. A method as defined in claim 1, wherein the orifice is part of
the nozzle.
3. A method as defined in claim 1, wherein the orifice is
positioned upstream from the nozzle.
4. A method as defined in claim 1, wherein the fluid is passed
through a tortuous path upstream from the nozzle, the method
further comprising the step of sensing a pressure drop over the
tortuous path for determining a fluid extensional viscosity of the
fluid.
5. A method as defined in claim 4, wherein the tortuous path
comprises a packed bed.
6. A method as defined in claim 1, wherein the controlled
conditions further comprises emitting the fluid from the nozzel at
a known temperature.
7. A method as defined in claim 1, further comprising the step of
optically inspecting a flow pattern being emitted by the nozzle in
order to further determine the atomization properties of the fluid
being emitted from the nozzle.
8. A system for determining the atomization characteristics of a
fluid comprising: a supply reservoir for holding a fluid, said
reservoir including an outlet for dispensing the fluid; a pumping
device for pumping the fluid from the supply reservoir; a nozzle
placed in communication with the supply reservoir for receiving the
fluid, the fluid being pumped from the supply reservoir by the
pumping device through the nozzle; a vibration sensor for sensing
vibrations occurring within the fluid nozzle as the fluid is being
emitted by the nozzle; a controller in communication with the
vibration sensor for receiving a spray pattern vibration output
from the vibration sensor, the controller being configured to
compare the sensed vibration s received from the vibration sensor
to the vibrations of a known reference fluid having known
atomization properties for determining the relative atomization
properties of the fluid being emitted from the nozzle; and a fluid
pressure drop over an orifice while the fluid is being emitted from
the nozzle, the pressure sensor being in communication with the
controller for determining a fluid shear viscosity.
9. A system as defined in claim 8, wherein the orifice is contained
in the nozzle.
10. A system as defined in claim 8, wherein the orifice is
positioned upstream from the nozzle.
11. A system as defined in claim 8, wherein the system includes a
tortuous path located between the supply reservoir and the nozzle
and wherein the system further comprises a pressure sensor that
senses a pressure drop over the tortuous path, the pressure sensor
being in communication with the controller for calculating a fluid
extensional viscosity.
12. A system as defined in claim 11, wherein the tortuous path
comprises a packed bed.
13. A system as defined in claim 8, further comprising a
temperature sensor for sensing the temperature of the fluid within
the supply reservoir.
14. A system as defined in claim 8, further comprising a spray
chamber into which the fluid is emitted exiting the nozzle, the
system further comprising an optical sensor for optically
inspecting a flow pattern being emitted from the nozzle.
Description
BACKGROUND OF THE INVENTION
The performance of spraying systems, as measured by the droplet
size spectra and distribution pattern of the spray is highly
dependent on the fluid properties of the liquid being sprayed. The
classic fluid properties such as density, equilibrium surface
tension, dynamic surface tension, shear viscosity, extensional
viscosity, void fraction of incorporated gasses, etc., all affect
the behavior of the liquid as it passes through an atomizer, and
subsequently, the characteristics of the resulting spray. When
sprays are produced for coating, drying and other processes, the
spray characteristics are critical factors in the performance of
the process and using the spray and the resulting quality of the
product.
To achieve desired spray characteristics, the proper nozzle or
atomizer must be selected and the optimal operating conditions of
the atomizer and fluid handling system must be determined for the
fluid to be atomized. Selection of the nozzle and determination of
the operating conditions can be an extensive, iterative,
experimental process due to the complexity of the fluid--atomizer
interaction. Especially for complex fluids that are heterogeneous,
non-Newtonian or otherwise difficult to characterize, a priori
predictions of sprayer performance can be difficult and inaccurate.
Subsequent changes in the fluid composition, wear in the atomizer
or other departures from the original test conditions can require
repeat experiments.
Laboratory measurements of fluid properties can be tedious,
expensive and time consuming. Additionally, the measurements are
often made using standardized techniques that do not closely
approximate the conditions in the actual spraying process. These
conditions can include turbulence in the flow system, shear rates
during flow and atomization, spatial and temporal gradient in
temperature, reactions in the fluid, etc.
Likewise, the measurement of spray characteristics such as droplet
size spectra, spatial distributions and patterns and droplet
velocities requires specialized, expensive equipment and technical
expertise in proper sampling in data interpretation. With limited
feedback on atomizer performance, especially in processes where the
sprays or products are not visible to system operators, generation
of poor quality sprays with undesirable characteristics is often
undetected until adverse consequences have occurred.
While these challenges are present for any spraying applications, a
particular problem exists for agricultural spraying where the spray
fluids can be mixtures of pesticides, fertilizers, surfactants,
shear-inhibitors, buffers, adhesives and other supplemental agents
known as spray adjuvants. These mixtures are highly variable and
often created for specific fields to be treated; the physical
properties of these mixtures are very complex and it is difficult
to predict how the fluid mixtures will behave in a given spray
system.
Spray drift, or the inadvertent movement of small spray droplets
from the target site to a non-target area, is a significant issue
presently facing agricultural applicators throughout the United
States. The strongly related issues of spray quality, that is,
coverage of the target and efficacy of the product against the
target pests are also of great concern. Agricultural applicators
desire to use the best drift management methods and equipment to
provide the safest and most efficient applications of pest control
materials to the targeted pest. They are responsible for making
good decisions in the field on a daily basis. Spray droplets that
drift off-site or are not correctly applied to the target crop or
pest represent wasted time, resources and result in environmental
pollution. This results in increased costs for the crop grower and,
subsequently, to the consumer. In addition, materials such as
herbicides and defoliants that drift off-site can result in a
serious financial liability if surrounding crops are damaged.
The minimization of off-site movement of agricultural sprays is to
the benefit of all concerned--applicators, farmers, regulators, the
public and the environment. Applicators need additional methods and
equipment to balance or optimize spray tank adjuvant performance
and economics to achieve drift mitigation goals for a given
application. In particular, a need currently exists for an
apparatus and method for assisting applicators in determining the
best possible application parameters to help meet product
instructional label criteria and mitigate spray drift.
It has long been understood that spray droplet size is the most
important variable in spray coverage, performance and spray drift
control or mitigation. For an agricultural spray dispensed from an
aircraft, spray nozzle selection is the first factor considered
when attempting to influence the spray droplet spectrum. Second are
the operational factors that influence atomization. These include
nozzle angle or deflection to the airstream, aircraft speed, and
spray liquid pressure. Spray tank additives or adjuvants play an
auxiliary role in spray droplet spectra. There are currently over
416 adjuvants marketed in California alone according to Crop Data
Management Systems (Marysville, Calif.). Adjuvants are classified
as surfactants, spreaders, stickers, deposition aids, activators,
humectants, antifoamers, wetting agent, and drift reduction agents.
These agents are added to the spray tank mix that may include a
number of active ingredients in the pesticide formulations.
Adjuvants can aid in the product making better contact with the
pest by spreading it over the leaf surface or the body of the
insect pest. Adjuvants can also reduce the likelihood of the
product dripping off the leaf onto the ground. Similarly, excessive
or incorrect adjuvant use can cause the product to drip or run off
the leaf. Adjuvants also can be very useful in helping the product
"stick" to the leaf or crop, preventing runoff during rain or
irrigation. Finally, adjuvants are often marketed as drift
reduction agents. The addition of an appropriate adjuvant can tend
to increase droplet size, which generally reduces driftable fines.
Unfortunately for applicators, sometimes recommended mixtures are
found to be "poor combinations", even if applied under "ideal
climatic conditions", when damage to crops, crop losses and drift
problems are experienced.
Droplet size is determined by the physical properties of the
components of the droplet fluid--in this case, the tank mix,
usually composed of water, pesticide active ingredient formulations
and adjuvant(s). The key properties of the tank mix that have a
significant effect on droplet size and the resulting atomization
profile are: dynamic and equilibrium surface tension, extensional
viscosity, and shear viscosity. Each time the applicator adds
something to the tank mix, the physical properties of that tank mix
change and that changes the atomization profile. Because of the
continued development and advancements in adjuvants, a need also
exists for a system and method for assisting applicators in making
sound decisions about the addition of these products and the
subsequent impact their addition will have on the actual
application, both for spray quality and for drift potential.
What is needed by all applicators, not just aerial but also for
field crop boom applicators and orchard and vineyard air carrier
applicators, is a field method to estimate the atomization
characteristics of particular spray mixes that they are about to
apply, especially if the mix is used only occasionally. By knowing
the atomization characteristics of the mix, one can then choose the
proper nozzle and spray conditions to avoid drift and optimize
deposit and efficacy. One may even, upon getting the information,
decide to delay an application until better environmental
conditions exist.
In a broader sense beyond pesticide spraying, optimizing any
spraying system requires that the atomizing properties of the fluid
be known. The complexity of fluid properties and the complexity of
the fluid-nozzle interaction make the prediction of the atomizing
properties from laboratory measurements of individually-measured
fluid properties (e.g., dynamic and equilibrium surface tension,
shear viscosity, extensional viscosity, density, etc.) difficult
and inaccurate. The difficulty of selecting and conducting the most
appropriate laboratory tests of the fluid properties, combined with
the uncertainty of prediction models of droplet size spectra from
the resulting measurements, lead to the need for a more direct and
simple method for the end user to determine atomization
characteristics of a fluid before undertaking a spray
operation.
SUMMARY OF THE INVENTION
The present disclosure is directed toward a system and method to
characterize the atomization properties of fluids in order to
select, optimize, maintain and control the proper nozzle and spray
conditions to achieve a desired spray with specified properties.
Additionally, the system may be used to determine if changes in a
fluid mixture will produce significant changes in the fluid
behavior as it passed through an atomizer. By characterizing the
atomization properties of fluids, the present disclosure allows a
user to control droplet size and droplet spectra in order to
minimize drift and to assist in applying the fluid onto a target
site.
In one embodiment, the system of the present invention can include
an orifice or nozzle similar or identical to a spray nozzle to be
used for spraying. The fluid is excited by being forced through the
nozzle under a controlled pressure or controlled flowrate and the
resulting vibrations of the fluid sheet or jet are detected by a
sensor. The sensor is in communication with a controller that
determines the characteristics of the vibration. These
characteristics can include the magnitude of the vibrations, the
directions of the vibration, the spectral composition of the
vibrations, the transmission of the vibrations through the fluid or
combinations of the characteristics. In one embodiment, the sensed
characteristics of a fluid to be tested are compared to the
characteristics measured for a fluid of known composition and
atomization properties. The relative atomization properties are
then determined.
In one embodiment, the test orifice and the flowrate of the test
fluid are adjusted to approximate known atomization regimes such as
those shown in FIG. 1. The flow rates and orifice diameters are
adjusted to cover a working range of the dimensionless numbers,
Reynolds (Re), Weber (We) and Ohneserge (Oh), that define the
fundamental map of atomization. (Re=Dv.rho./.mu.;
We=Dv.sup.2.rho./.sigma.; Oh=We.sup.1/2/Re where D=characteristic
diameter, v=characteristic velocity, .rho.=fluid density,
.mu.=fluid viscosity and .sigma.=fluid surface tension). When fluid
properties are unknown, these numbers can be estimated from a
priori knowledge or approximated with values from similar
fluid.
In one embodiment, a positive displacement pump is in communication
with the controller and is adjusted to vary the fluid flow rate
through the orifice in a programmed sequence, representing a range
of fluid velocities through the orifice. The microcontroller
receives the vibration data from the sensor simultaneously and
determines the fluid vibration properties as a function of the
liquid velocity and flowrate through the orifice.
In general, the method of the present disclosure for determining
the atomization characteristics of a fluid being emitted by a
nozzle includes the steps of first emitting a fluid from a nozzle
at controlled conditions. Vibrations occurring within the fluid
nozzle are then sensed while the fluid is being emitted. The sensed
vibrations are then compared to the vibrations of a known fluid
having known atomization properties for determining the relative
atomization properties of the fluid being emitted from the nozzle.
The controlled conditions at which the fluid is emitted from the
nozzle may include a known flow rate, temperature, pressure, and
the like. The controlled conditions can be known by placing various
sensors within the fluid flow path. For instance, the system may
include a flow meter, one or more temperature sensors, and one or
more pressure sensors that are each placed in communication with a
controller that also receives the sensed vibrations in determining
the relative atomization properties of the fluid. The controller
may be, for instance, one or more microprocessors.
In one embodiment, the method may include the step of sensing a
fluid pressure drop over an orifice while the fluid is being
emitted from the nozzle. The pressure drop may be communicated to a
controller for determining a fluid shear viscosity and a density of
the fluid. The orifice over which the pressure drop is sensed may
comprise the nozzle itself or may be positioned upstream from the
nozzle.
In addition to sensing fluid pressure over an orifice, a fluid
pressure drop may also be sensed over a tortuous path through which
the fluid flows. The tortuous path may be positioned upstream from
the nozzle and, in one embodiment, may comprise a packed bed. By
sensing the pressure drop over the tortuous path, a fluid
extensional viscosity may be determined.
In one embodiment, the vibrations that are sensed from the nozzle
are converted into a spectral density that is used to determine a
power spectrum. The power spectrum is then compared to the power
spectrum of one or more reference fluids for determining the
relative atomization properties of the fluid. For example, in one
embodiment, the sensed vibrations are compared to the vibrations of
a plurality of known fluids. The known fluids may include, for
instance, a relatively low viscosity fluid, a relatively high
viscosity fluid, and a fluid having a viscosity in between the
relatively low viscosity fluid and the relatively high viscosity
fluid.
Once the relative atomization properties of the fluid are
determined, one can select a nozzle and operating conditions for
emitting the fluid from the selected nozzle in a fluid application
process as desired. Basically, the atomization properties of the
fluid may be determined for any suitable process in which the fluid
is to be emitted from a nozzle. In one particular embodiment, for
instance, the atomization properties of the fluid are determined
for applying the fluid in an agricultural process. The fluid, for
instance, may comprise a pesticide, a herbicide, a fertilizer, or
any other similar material. In agricultural processes, for example,
the fluid may be emitted from a nozzle that is mounted to a boom
that is in turn pulled by a tractor or may be emitted by a nozzle
mounted to an aircraft.
In general, any suitable device may be used in order to sense the
nozzle vibrations as the fluid is being emitted from the nozzle.
For example, in one embodiment, an accelerometer may be used. The
accelerometer may sense vibrations in a single direction or in
multiple directions.
In one embodiment, the fluid is emitted through the nozzle and into
a spray chamber. An optical device, such as any suitable camera,
may be used to optically inspect a flow pattern being emitted by
the nozzle. The flow pattern may be further used to characterize
the atomization characteristics of the fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is the classic map of liquid atomization regimes showing
predominant mode of breakup versus the orifice flow nondimensional
numbers, Re and We;
FIG. 2 is a plan view of one embodiment of a system made in
accordance with the present invention;
FIG. 3 is a perspective view of one embodiment of a vibration
sensor attached to a nozzle for use in accordance with the present
invention;
FIG. 4 is a graphical representation of the results obtained in
Example 1;
FIGS. 5A and B represent a side view and a perspective view of the
nozzle tested according to Example 2 below; and
FIGS. 6-14 are graphical representations of the results obtained in
Example 2.
DETAILED DESCRIPTION
In general, the present invention is directed to a system and
process for determining the atomization properties of complex
fluids without the need for direct measurement of physical
properties or spray droplet size spectra, spray pattern or droplet
velocities. More particularly, in one embodiment, the fluid to be
characterized is pumped through an orifice and the resulting
vibration of the fluid flow is measured by a sensor. In one
embodiment, the pressure drop of the fluid across the test orifice
is simultaneously measured in order to provide an estimate of the
shear viscosity of the fluid and the pressure drop across a
tortuous path, such as across a packed bed of screens, is measured
in order to provide an indication of the extensional viscosity.
In one embodiment, the system may be designed to be sufficiently
simple and small so that sprayer operators in industries such as
agricultural field spraying can use the system in field conditions
using only a small sample of the spray fluid to be dispensed. After
characterization of the fluid, they can select the optimal spray
nozzle or operating conditions to produce the desired spray
characteristics. For example, they may use the system to test a
spray liquid mixture composed of various components in order to
select a nozzle to minimize spray drift during application to a
field. It should be understood, however, that in addition to
agricultural applications, the method and system of the present
invention may be used to characterize and determine the atomization
properties of fluids in any suitable process in which the fluid is
to be emitted from a nozzle. For example, in one embodiment, the
method and system of the present invention may be incorporated into
a paint spraying operation.
Referring to FIG. 2, one embodiment of a system made in accordance
with the present invention is shown. As illustrated, the system
includes a supply reservoir 10 in which the fluid to be tested is
contained. In general, any suitable fluid may be tested in
accordance with the present invention. The fluid, for instance, may
contain various ingredients including suspended particles. Further,
the fluid may be adapted for use in any process as desired. For
example, in one embodiment, the fluid may comprise a pesticide,
herbicide or fertilizer that is to be applied during an
agricultural spray process. In an alternative embodiment, the fluid
may comprise a fuel. For instance, the present invention may be
used to characterize the atomization properties of fuels when the
fuels are being injected into an engine.
The fluid contained in the supply reservoir 10 is pumped from the
supply reservoir in this embodiment by a pumping device 12. In
general, any suitable pumping device may be used. In one
embodiment, for instance, the pumping device 12 may comprise a
positive displacement pump that is capable of pumping the fluid
from the supply reservoir in controlled amounts. As shown in FIG.
2, the fluid contained in the supply reservoir is pumped through a
test nozzle 14 to produce a sheet, jet or spray 16 that may
optionally be collected in a collection reservoir 18.
In order to ensure that the fluid is pumped through the system at a
controlled temperature, the supply reservoir may be placed in
communication with a temperature control unit 20 that is configured
to maintain the fluid at a specified temperature. Alternatively, a
temperature sensor may be placed within the system in order to
simply know the temperature of the fluid as it is being emitted by
the nozzle 14.
In accordance with the present invention, a vibration sensor 22 is
placed in association with the nozzle 14 for sensing vibrations
within the nozzle as the fluid is being emitted by the nozzle.
The vibration sensed by the vibration sensor 22 can provide much
information about the properties of the fluid and specifically the
atomization properties of the fluid being emitted by the nozzle.
For instance, it is known that flowing fluids that interact with
structures or nozzles produce characteristic vibrations. The
fundamental process is the periodic separation of the boundary
layer of flow passed any structure with sufficiently bluff trailing
edges. The fluid properties of surface tension (dynamic and
equilibrium) and viscosity (shear and extensional or elongational)
affect the behavior of the fluid flow and breakup. Of particular
significance, the vibrational frequencies that are sensed along
with certain vectors of the vibration provide flow rate and droplet
size information about the fluid as it is emitted from the
particular nozzle.
In general, any suitable fluid nozzle may be monitored according to
the present invention. For instance, the fluid nozzle may emit a
fan-type spray pattern or a conical spray pattern. Different
nozzles will emit certain frequencies of vibration. Thus, the
reference nozzle should generally be similar to the test
nozzle.
In addition to testing different types of nozzles, both
continuously flowing fluid nozzles and pulsed fluid nozzles may be
used in the system and process of the present invention. When used
in conjunction with pulsed nozzles, the vibration analysis is
capable of separating vibrations due to atomization properties from
vibrations due to pulsation.
Examples of nozzles that may be used as test nozzles in the system
of the present invention include metering orifice plates that are
commercially available from the TeeJet Company. The orifice plates
are available in a range of sizes from 0.008 inches to 0.250 inches
in diameter. The metering plates represent an abrupt, sharp
orifice. Straight stream nozzles may also be used and are available
from the Spraying Systems Company. Such straight stream nozzles are
available in orifice diameters of from 0.041 inches to 1.375 inches
and provide a smooth flow transition prior to the orifice. In still
another embodiment, fan nozzles may be used to produce liquid
sheets. Industrial fan nozzles are available in fan angles of
15.degree., 25.degree., 40.degree., 50.degree., 65.degree.,
73.degree., 80.degree., 95.degree., 110.degree., and the like. The
fan nozzles can have an equivalent orifice diameter of 0.011 inches
to 1.375 inches.
Air inclusion nozzles may also be used. Air inclusion nozzles
produce a more complex flow passageway and are commonly used in the
ground application industry. Air inclusion nozzles typically
produce vibration profiles that have an amplitude approximately two
orders of magnitude greater than conventional nozzles. Air
inclusion nozzles are also sensitive to flow conditions such as
nozzle clogging.
When testing fluids for agricultural spray applications, typically
the spray nozzles include fan nozzles that have flow angle ranges
from 40.degree. to 110.degree. and flow ranges from about 0.1
gallons per minute to 1.0 gallons per minute (at 40 psi standard
pressure).
In one embodiment, flow conditioning sections may be incorporated
into the system in order to produce low turbulence as the fluid
enters the nozzle area. Flow conditioning can be as simple as a
straight section of smooth tube or may include more orifice
diameters upstream of the nozzle. Alternatively, an array of
straightening tubes constructed of, for instance, thin wall
stainless steel tubing, can be packed to create more laminar flow
section prior to nozzle.
Referring to FIG. 3, one exemplary embodiment of a fan nozzle 30
that may be used as a test nozzle in accordance with the present
invention is shown. Nozzle 30 as illustrated in FIG. 3 is a typical
nozzle used in agricultural applications.
As also illustrated in FIG. 3, a vibration sensor 32 is mounted on
the nozzle for sensing vibrations. Various different types of
vibration sensors may be used in accordance with the present
invention. For example, in one embodiment, an accelerometer may be
used. The vibration sensor may be configured to sense vibrations in
a single direction, or in multiple directions, such as triaxial
accelerometers.
When sensing vibrations in multiple directions, it has been
discovered that each direction may provide different information
regarding the properties of the fluid and/or the properties of the
nozzle. As shown in FIG. 3, as used herein, the Z-axis or direction
comprises the direction of flow of a fluid through the nozzle. For
instance, if the nozzle is pointing downward, the Z-axis comprises
a vertical line. The X-axis, on the other hand, is perpendicular to
the Z-axis and extends to the left and right of the nozzle when
facing a front of the nozzle. The remaining axis, the Y-axis, is
perpendicular to the Z-axis and to the X-axis. When sensing
vibrations, the Y-axis typically provides information related to
atomization and spray quality. The Z-axis provides information
related to flow rate, while the X-axis provides information related
to pulse valve operation when the valve is pulsating.
Some examples of vibration sensors that may be used in the present
invention include any suitable accelerometer including
piezoelectric films.
Referring back to FIG. 2, the vibration sensor 22 may be placed in
any appropriate location on the nozzle 14 for sensing vibrations.
For instance, the vibration sensor 22 can be placed on the nozzle
housing or, alternatively, can be otherwise incorporated into the
body of the nozzle. In some applications, it has been found that
the vibration sensor can also be placed upstream from the nozzle
and still be capable of registering vibration frequencies.
Once the vibration sensor 22 measures vibrations from the fluid
nozzle 14, the signal created by the sensor is fed to a controller
24 for analysis. The controller 24 may comprise, for instance, a
microprocessor or a plurality of microprocessors. The controller
24, for instance, may be used to determine peak vibration, duration
of vibration and the spectral composition of the vibration. In one
embodiment, for instance, the signal created by the vibration
sensor 22 can be manipulated and conditioned. For example, the
nozzle vibration can be measured and a spectral analysis, such as a
Fast Fourier Transform, is conducted to determine a power spectrum.
The power spectrum can then be analyzed and compared to the power
spectrum of a reference fluid that has known atomization
properties. In this manner, the atomization properties of the fluid
being fed through the system can be determined.
In one particular embodiment, for instance, the controller 24 may
store the atomization properties of multiple fluids that each have
different viscosities. For instance, the controller may include the
atomization characteristics of a reference fluid having a
relatively low viscosity, a reference fluid having a relatively
high viscosity, and a reference fluid that has a viscosity in
between the relatively low viscosity fluid and the relatively high
viscosity fluid. Of course, the atomization characteristics of many
other fluids may be stored within the microprocessor 24. By
comparing the vibration patterns of the fluid being emitted by the
nozzle 14 to the known atomization properties of the reference
fluids, relatively accurate estimations can be made regarding
droplet size and/or the spray pattern of the fluid as a function of
flow rate and process conditions.
As shown in FIG. 2, the system of the present invention can further
include a flow meter 26 and one or more pressure sensors 28. The
flow meter may be placed in communication with the controller in
order to provide the controller with the flow rate of the fluid
being emitted through the nozzle 14. As also shown, the controller
24 may be used to control and receive information from various
other components in the system. For instance, the controller 24 may
receive information and control the pumping device 12 and may
receive information or control the temperature control unit 20.
The pressure sensor 28 as shown in FIG. 2 may also be in
communication with the controller 24. The pressure sensor 28 in one
embodiment, may determine the pressure drop of the fluid across the
nozzle 14. When coordinated with the pumping device 12, the
pressure drop versus flow rate information provides an estimate of
the fluid shear viscosity and density independently from the fluid
vibration data.
Instead of measuring the pressure drop across the nozzle 14, in an
alternative embodiment, an orifice may be positioned upstream from
the nozzle 14. The pressure sensor 28 may determine the pressure
drop against the orifice for also determining fluid shear viscosity
and density.
In still another embodiment of the present invention, this system
can include a tortuous path positioned in between the supply
reservoir 10 and the fluid nozzle 14. The tortuous path, for
instance, may comprise a packed bed, such as a packed bed of
screens. An additional pressure sensor may be positioned to
determine the pressure drop of the fluid over the tortuous path.
When coordinated with the pumping device 12 and/or the flow meter
26, the pressure drop over the tortuous path versus flow rate
information provides an estimate of the fluid extensional viscosity
independently from the fluid vibration data.
When the system includes the pressure sensor 28 as shown in FIG. 2,
as described above, information from the pressure sensor and the
flow meter 26 may be used in conjunction with the geometry of the
nozzle 14 to characterize the shear viscosity of the fluid. A
simple equation relating flow rate of a fluid through an orifice to
the pressure drop through the orifice is m=C.sub.dA.sub.t(2.rho.
.DELTA.p/).sup.1/2 where m=mass flowrate, C.sub.d is a drag
coefficient related to the fluid and the orifice characteristics
and A.sub.t is a characteristic of the test nozzle 14, .DELTA.p=the
measured pressure drop across the orifice and .rho.=the density of
the fluid. The C.sub.d term is a function of Reynolds Number
(Re=Dv.rho./.mu. where D=characteristic diameter, v=characteristic
velocity, .rho.=fluid density and .mu.=fluid viscosity). When the
test nozzle 14 is installed, the orifice characteristics are known.
Therefore, knowing the flowrate from the flowmeter and the pressure
drop across the orifice from the pressure sensor, a term for the
fluid density and viscosity can be calculated using iteration. This
information can be used in characterizing the fluid, especially
when considered in conjunction with the vibration data from flow
through the orifice.
As described above, in one embodiment, the vibration information
received from the vibration sensor may be converted into a power
spectrum for comparison to the power spectrum of various reference
fluids under similar conditions. For many nozzles, such as
especially nozzles used in the agricultural industry, the nozzles
produce characteristic vibrations in the range of from about 4 kHz
to about 6 kHz bands. In general, a higher power spectrum indicates
better atomization and usually smaller droplet size.
In one embodiment, the pumping device 12 as shown in FIG. 2 may be
configured to vary the flow rate of the fluid being tested in a
programmed sequence. For instance, the controller 24 may be placed
in communication with the pumping device 12 for varying the flow
rate in a predetermined manner. By varying the flow rate in a
programmed sequence, vibrations generated by the fluid flowing
through the nozzle can be determined as a function of velocity. In
this manner, the atomization properties of the fluid can be
determined also as a function of velocity and/or flow rate with
respect to the test nozzle.
In addition to the vibration sensor 22 as shown in FIG. 2, the
system can further include an optical sensor positioned to observe
the spray pattern 16 that is emitted from the nozzle 14. In
general, any suitable optical sensor may be used, such as an array
of LED lights in conjunction with light sensors, or may comprise
one or more cameras. The optical sensor may be configured to
inspect the spray or sheet 16 being emitted from the nozzle to
determine or measure the shape of the spray. For instance, a narrow
spray width may indicate larger droplet size. This information can
then be used in conjunction with the information received from the
vibration sensor.
The present invention may be better understood with respect to the
following examples.
EXAMPLE NO. 1
A number of fluids were sprayed through a TeeJet XR11004 fan
nozzle. The fan nozzle tested had a 110.degree. flow angle which
refers to the extent of the fan-like shape within the X-Z axis
plane. The nozzle also had a 0.4 gallon per minute flow rate at 40
psi liquid supply pressure. Fluid was supplied to the nozzle at 40
psi (276 kPa). A single chip accelerometer (Analog Devices ADXL
311) was mounted on the nozzle body to sense the vibration along
the axis normal to the fan (the "Y" axis as shown in FIG. 3). Data
were collected for 2 seconds and a Discrete Fourier Transform was
performed on the data by an on-board microprocessor to produce the
power spectrum of the signal.
Results for tap water, a viscous fluid (thick sugar syrup), a low
surface tension fluid (water+1% dishwashing detergent) and a fluid
with polymer-like properties (fat free salad dressing--with guar
gum and other thickeners) are shown in FIG. 4. Differences in the
spectra for the fluids were apparent, especially in the 2.5-4.5 and
5-8 kHz frequency bands and when considering that the dB response
axis is a log scale.
As shown by the results in FIG. 4, a relationship does exist
between frequency and viscosity of fluids being emitted by a
nozzle.
EXAMPLE NO. 2
The potential simplicity and an inexpensive embodiment of the
invention was demonstrated using a manually-actuated piston pump
and close-coupled spray nozzle as shown in FIG. 5. A triaxial
accelerometer (PCB Model 356A22) was coupled to the outlet of the
spray nozzle. The integrated pump was a positive displacement
piston pump that dispensed 0.8 ml/stroke. The nozzle was a fixed
orifice producing a hollow cone spray. Four fluids were tested to
determine the vibration characteristics and the resulting spray
droplet size, as visualized by adding a dye to the spray liquid and
photographing the spray deposit.
The reference fluid was municipal water. The test fluids were 40%
ethyl alcohol, a commercial spray surface cleaner (Formula 409) and
glycerin. Results for water appear in FIG. 6; results for ethyl
alcohol appear in FIG. 7; results for the spray cleaner appear in
FIG. 8; and results for glycerin appear in FIG. 9. A clear
relationship between the relative power in the 4-6 kHz frequency
band and the resulting spray droplet size was observed.
For each of the test fluids, an image of the spray deposit was
captured and the resulting droplet size spectra based on number
counts of droplet stains in the image was recorded. Specifically,
the spray deposition pattern and the droplet size spectra for water
is shown in FIG. 10, the spray deposition pattern and droplet size
spectra for ethynol is shown in FIG. 11, and the spray deposition
pattern and droplet size spectra for the cleaner is shown in FIG.
12. Glycerin, on the other hand, failed to atomize and did not
produce a spray at all.
As can be shown in FIGS. 10-12, water had a very small droplet size
that was smaller than the droplet size of the ethyl alcohol and
smaller than the droplet size of the spray cleaner. The droplet
size of the ethyl alcohol was smaller but comparable to the droplet
size of the spray cleaner. Thus, as shown in FIGS. 6-9 in
comparison to FIGS. 10-12, as the power increased, the droplet size
decreased. The glycerin was not atomized by the pump-nozzle
combination; the resulting vibration data indicated virtually no
vibration in the 4-6 kHz band.
From the deposition images for water, ethynol and spray cleaner,
the size distribution of the stains on the target paper were
analyzed by image analysis, a common technique used to measure and
characterize spray deposition. The number of stains in a
representative area of target were categorized by size and counted
to produce the results illustrated in FIG. 13.
As shown in FIG. 13, from the distribution, the fraction of
droplets (by number) below a cutoff size of 100 microns was
determined. This number was then compared to the spectral density
of the vibrations illustrated in FIGS. 6, 7 and 8. The areas under
the vibration curves of the power spectra were integrated over the
range of 4-6 kHz, the frequency band most closely associated with
the atomization. The relationship between the fraction of droplets
and the small size ranges and the total vibration in the 4-6 kHz
range is shown in FIG. 14. A strong relationship between vibration
and droplet size spectra can be seen.
These and other modifications and variations to the present
invention may be practiced by those of ordinary skill in the art,
without departing from the spirit and scope of the present
invention, which is more particularly set forth in the appended
claims. In addition, it should be understood that aspects of the
various embodiments may be interchanged both in whole or in part.
Furthermore, those of ordinary skill in the art will appreciate
that the foregoing description is by way of example only, and is
not intended to limit the invention so further described in such
appended claims.
* * * * *